The field of the invention is, in general terms, that of automobile lights. In this field, various types of light device are known, amongst which there are essentially:                parking lights, of low intensity and range;        passing, or dipped, headlights, with greater intensity and range on the road of around 70 meters, which are used essentially at night and where the distribution of the light beam is such that it makes it possible not to dazzle the driver of a vehicle being passed;        long-range headlights, and supplementary lights of the long-range type, where the area of vision on the road is around 200 meters, and which must be switched off when passing another vehicle in order not to dazzle its driver;        fog lights.        
In addition, an improved type of light is known, referred to as a dual-function light, which combines the functions of dipped and long-range lights: for this purpose, it is possible for example to dispose inside the dual-function light a movable shield, for example a metallic plate, able to move on command from a first position in which it obscures part of the light signal produced by the light source of the light, the range or the light being thus limited to that of dipped headlights in order not to dazzle the other drivers, to a second position in which it does not obscure the light signal produced by the light source of the light, the range of the corresponding light then being that of main beam headlights. This example embodiment is principally used in light devices of the elliptic type.
A particular type of light is also known which makes it possible, in particular at night, to obtain a visible image of the road on a monitoring screen. This type of light is in fact a light of the main beam type, equipped with a tilting infrared filter, which can on command move from a first position in which it filters all the light signals produced by the light source of the light, so that only the non-dazzling infrared rays effectively emerge from the light device, to a second position in which the filter does not obscure any light signal produced by the light source of the light, the range of the light then corresponding to that of main-beam lights.
In the context of the invention, the movable shield and the infrared filter are two particular examples of a pivoting plate equipping the light devices according to the invention. In general terms, the devices to which the invention relates are all those which are capable of being equipped with a pivoting plate, independently of the function fulfilled by the said pivoting plate, capable of tilting between two operating positions.
One example of such a known device of the state of art is shown, in section and plan view, in FIG. 1. The example depicted corresponds to a headlight 110, of the elliptic type, equipped with an infrared filter 103. The headlight 110 comprises essentially a reflector 100, a light source 101, emitting light signals 108, disposed close to the apex of the reflector 100, and an exit lens 102 disposed so as to obtain a light beam satisfying the requirements of the various standards. The light signals 108 are emitted either directly towards the exit surface 102, or indirectly after having undergone any diversion and/or reflections. The infrared filter 103 is disposed in the headlight 110. The infrared filter 103 is movable, that is to say capable of moving between a first approximately vertical position 105 in the figure, referred to as the active position, in which the majority of the light signals emitted by the light source 101 pass through the filter 103, and a second position 104 approximately horizontal in the figure, referred to as the passive position, in which none of the light signals emitted by the light source 101 passes through the filter 103. Each filter 103 can consist of a plate of rectangular or circular shape able to pivot about a rotation axis 106, for example attached to a housing 107 constituting the enclosure of the headlight 110. The rotation axis 106 is driven by a motor 109, which makes it possible to make the filter 103 tilt from the first position 105 to the second position 104.
The various standards in force require the pivoting plates, disposed in the light devices, whether it is a case of an infrared filter or a movable shield, to return to a secure position in the case of malfunctioning of the light device in question. The secure position is that in which the light device causes the least possible nuisance for the other drivers. As it happens, in both cases, the secure position corresponds to the first vertical position of the pivoting plate within the light device. In the state of the art, illustrated in FIG. 2, when a malfunctioning of the motor 109 occurs, a return spring 200 automatically returns the pivoting plate, for example the infrared filter 103, into the secure position.
In the state of the art, in order to make the pivoting plate 105 move, an actuator 109 of the solenoid type is normally used, rotary or linear, whose main quality is longevity. However, the use of solenoid motors in light devices presents a certain number of drawbacks: this type of actuator is very bulky, particularly heavy, and its operating characteristics depend greatly on the variations in temperature in the environment in which it functions.
It is an object of the invention to respond to all the drawbacks which have just been mentioned. To this end, according to the invention, a light device is proposed equipped with a DC motor for causing the tilting of a pivoting plate. In addition, in the invention, a solution is proposed for preventing the DC motor from degrading too rapidly. This is because the risks of degradation of a DC motor are greater than those incurred with a solenoid motor: once the pivoting plate has been brought into its second position, the DC motor begins a so-called holding phase, in locked torque, in order to keep the pivoting plate in the second position. During this phase, the DC motor behaves electrically like a simple resistor. Its current consumption then increases greatly, the power to be dissipated then rapidly becoming too great to ensure the integrity of the motor. In the invention, it is therefore proposed to limit the motor supply current, for example by means of an electronic control card, at least during the phases where the DCT motor is functioning in locked torque.